Diffusion Mechanisms in the B2 Type Intermetallic Compounds

Abstract

The diffusion coefficients of A and B atoms in the B2 type AB alloy are derived for the case that highly correlated vacancy jump cycle (six-jump vacancy cycle) is operative. The effective jump frequency to complete the cycle is expressed in terms of frequencies for individual vacancy jumps; the calculation is made by applying the concept of the mean first passage time known in the theory of stochastic processes. On the basis of the analytical expression for the diffusion coefficients, the ratio of the diffusivities of the two constituent atoms and the isotope effect can be discussed quantitatively.